Drainage foil having a foil blade insert

ABSTRACT

A drainage foil assembly wherein a structural foil body having a top surface is provided with a plurality of end abutting foil blade inserts which form an upper leading edge and top bearing surface flush with the body top surface. The foil blade inserts are mounted to the foil body solely by the use of springs which urge each of the foil blade inserts into seated engagement with the foil body in the direction of wire travel. The blade top bearing surface is positionable against a traveling wire to induce drainage on the foil side.

United States Patent [1 1 Getman et al.

[ DRAINAGE FOIL HAVING A FOIL BLADE INSERT [75] Inventors: Darryl L.Getman, South Beloit; Marshall G. Swenson, Rockford,

both of 111.

[73] Assignee: Beloit Corporation, Beloit, Wis.

[22] Filed: Dec. 10, 1973 [211 Appl. No.: 423,628

Related U.S. Application Data [63] Continuation of Ser. No. 256,471, May24, 1972,

abandonedv [52] U.S. Cl. 162/352, 162/374 [51] Int. Cl. D2lf 7/00 [58]Field of Search 162/352, 374

[56] References Cited UNITED STATES PATENTS 3,140,225 7/1964 Truxa162/352 3,337,394 8/1967 White et a1. 162/374 3393,124 7/1968 Klingleret a1. 162/374 X 3,446,702 5/1969 Buchanan 162/374 3,574.056 4/1971 Jadet a1. 162/352 1 1 Mar. 11,1975

3,576,716 4/1971 Reynolds et al. 162/352 3,619,363 11/1971 Pherson162/352 3,732,142 5/1973 Beacom et al. 162/374 3,778,342 12/1973Charbonneau 162/352 FOREIGN PATENTS OR APPLICATIONS 1,958,758 6/1971Germany 162/374 Primary Examiner-S. Leon Bashore AssistantExaminer-Richard V. Fisher Attorney, Agent, or FirmDirk J. Veneman;Bruce L. Samlan; Gerald A. Mathews [57] ABSTRACT A drainage foilassembly wherein a structural foil body having a top surface is providedwith a plurality of end abutting foil blade inserts which form an upperleading edge and top bearing surface flush with the body top surface.The foil blade inserts are mounted to the foil body solely by the use ofsprings which urge each of the foil blade inserts into seated engagementwith the foil body in the direction of wire travel. The blade topbearing surface is positionable against a traveling wire to inducedrainage on the foil side.

11 Claims, 11 Drawing Figures PATENTEDHARI 1 I975 -SHEEI1UF3 3370597PATENTED 1 I975 3,870,597 sum 3 95 3 F/G. 6a (PRIOR ART) FIG. 6b (PRIORART) d d 54 d lll 56 55 T\\ F/G. 6c (PRIOR ART) F/G. 6d (PRIOR ART) F/G.6e (PRloR ART) DRAINAGE FOIL HAVING A FOIL BLADE INSERT This is acontinuation, of application Ser. No. 256,471, filed May 24, 1972, nowabandoned.

BACKGROUND OF THE INVENTION In the forming section of a papermakingmachine, such as the Fourdrinier type, water is removed through the wireon which the fiber-water slurry has been deposited by applying a foilblade to the opposite side of the wire. Usually, the leading edge of thefoil is angled slightly away from the oncoming wire as is the trailingportion of the foil. The top surface of the foil over which the wiretravels, and its leading edge, are sub jected to heavy wear. Thesesurfaces are made of, or coated with, wear resistant material such asaluminum oxide, tungsten carbide, silicon carbide and chromium oxide toresist abrasive wear as much as possible.

The leading edge skims off the water carried on the wire and thedownwardly angled rear portion of the foil produces a slight negativepressure differential on the foil side to induce entrained water to flowthrough the wire leaving the now considerably more dewatered fibrous maton the top wire surface.

The position and angles of the leading and trailing rear portions of thefoil are discussed more thorougly in U.S. Pat. No. 3,377,236 which iscommonly owned with this application and which is incorporated herein byreference.

Drainage foils extend across the width of a papermaking machine and canbe over 30 feet long. The first foils were of a one piece design and hadtheir top bearing surface coated with a ceramic or other abrasionresistant material which was usually sprayed on and polished. When thematerial wore away or was chipped or otherwise damaged, the whole foilhad to be removed from the machine and shipped to the manufacturer. Thiswas very time consuming and expensive. Whole extra foils had to beavailable for use while the other foils were being refitted withabrasion resistant material.

Improved foils were then developed wherein an abrasion resistant insertwas fitted on or over the foil body so that only the insert had to bereplaced. In some embodiments, the insert could be replaced while thefoil body remained in place on the machine. However, the inserts were aslong as the foil body itself and they were adhesively secured, screwedor wedged into the foil body, sometimes with dovetail joints, so thatthey were very difficult to remove. The abrasion resistant insert, orfoil blade, comprising the leading face and/or wire contacting topsurface of the drainage foil must be securely held to the foil body toprevent vibration or displacement since any such movement would beextremely detrimental to the formation of the web on the wire travelingover the foil.

Today, paper mills still have to store long lengths of brittle foilblade inserts, on which a small defect could ruin the entire blade, andthe manner in which they are fitted to the foil body makes replacement atime consuming process.

U.S. Pat. Nos. 3,140,225 and 3,520,775 illustrate the foil type having aremovable top cover of abrasion resistant material. U.S. Pat. No.3,393,124 shows a wear resistant insert adhesively secured to the foilbody. U.S. Pat. No. 3,446,702 illustrates a dovetailed insert wedgedinto the foil body. U.S. Pat. No. 3,619,363 and 3,535,204 illustrateother arrangements I wherein the foil blade is wedged into the foilbody.

A common problem with prior foil designs resides in the fact that thefoil blade insert material, such as aluminum oxide, and the foil bodymetal, such .as stainless steel, have different coefficients of thermalexpansion. Thus, during cleanup or even during normal operation, changesin the temperature of the water passing over the foil could cause thetwo materials to expand or contract to such an extent that they wouldbecome unsecured, in the case of adhesive bonding, or considerablyloosened or gapped if mechanically fastened to the foil body.

SUMMARY OF THE INVENTION This invention mitigates or obviates theaforementioned problems. Instead of a continuous piece of abrasionresistant material permanently, or near permanently, secured to thedrainage foil body, this invention provides a plurality of individualfoil blade segments aligned end to end along the entire foil body lengthwhich are individually and resiliently secured to the foil body in thedirection of wire travel. In this manner, expansion of the foil bladerelative to the foil body does not produce any looseness or gaps betweenthese parts. Further, by urging the foil blade against the foil bodywith a spring or springs in the direction of wire travel, there is nodanger a segment will fall out when the papermaking machine is shut downfor cleaning.

Individual foil blade segments can be replaced on site at the paper millwith relatively little effort at nominal expense since the whole foilblade need not be replaced. Spare foil blade segments can be easilyhandled, shipped and stored. The cumbersome foil body need not beremoved from the machine or sent to the manufacturer to be refitted withabrasion resistant inserts. Accordingly, it is an object of thisinvention to provide a drainage foil having an abrasion resistant foilblade which is easily and quickly replaceable.

Another object is to provide a drainage foil on which the foil blade isnot bolted or permanently or adhesively secured.

Still another object is to provide a drainage foil and a foil blade ofsimple design which are easy to manufacture and have a minimum of costlyfinished surfaces and held tolerances.

Still another object is to provide a drainage foil meeting all theaforementioned objectives and on which the abrasion resistant foil bladecomprises both the leading edge and top bearing surface of the foil.

A feature of this drainage foil is the use of a foil blade comprising aplurality of similar segments aligned and held end to end for the entirefoil length.

Another feature is the provision of a spring retaining each foil bladesegment onto the foil body.

Another feature is the positioning of a spring to urge each foil bladesegment into seated engagement with the foil body in the direction ofwire travel so that these parts will remain together in operatingposition without adhesives, bolts or mechanical wedges even when thewire is not moving.

These and other objects, features and advantages of the drainage foiland foil blade insert will be recognized as the description of thepreferred embodiments is read in conjunction with the attached drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of the drainage foilshowing the foil blade inserts aligned end to end and held with endsprings.

FIG. 2 is a side elevational view through section IIII of the foil inFIG. 1.

FIG. 3 is an enlargement of the foil body.

FIG. 3a is a cross sectional side view of a foil blade insert formounting in the foil body in FIG. 3.

FIG. 4 is a cross sectional side view of the foil blade insert and foilbody in FIGS. 3 and 3a assembled together.

FIG. 5 is a cross sectional side view of another embodiment of a foilblade insert.

FIG. 6a through 6e show cross sectional side views of various prior artconfigurations of foils.

PREFERRED EMBODIMENTS A drainage foil 10, commonly referred to as afoil, is shown in FIG. 1 as viewed from above on which a plurality offoil blade inserts 12 are mounted in end to end abutting adjacency ingroove 14 formed in the top leading corner thereof. The foil body 16,designed to resist deflection, is pivotally mounted in the formingsection of a paper making machine about journals 17, shownschematically, so that the top bearing surface 18 of the foil blade isbrought into skimming engagement with the wire on which a liquidcontaining fibers has been deposited by a headbox (not shown). The wireis indicated schematically by arrow 20 traveling in the indicateddirection, known as the machine direction (i.e., from the headbox to thereel on a paper making machine). The foil body, groove 14 and abuttingfoil blade inserts 12, extend transversely to the machine direction.

Adjoining blade inserts 12 are not fastened to one another, but areurged into contact at their butt joints 22 by restraining end springs 25mounted to the foil body 16 at either end thereof with screws 27 andresiliently biased against the outermost ends 23 of the outermost foilblade inserts 12. Square butt joints 22 are preferred between adjacentfoil blade inserts 12 since angled joints have a more pointed corneredge which is more susceptible to chipping and fracture. Also, foilblade inserts having angled end joints, with respect to the direction ofwire travel, would require special end foil blade pieces to hold thepointed ends in.

In the two embodiments shown in FIGS. 2 through 5, corresponding itemsare correspondingly numbered and suffixes a, b will be used todistinguish items in the assembled foils shown in FIGS. 4 and 5.Reference to a numeral in one figure will be understood to be referencealso to corresponding numerals in the other figures.

As shown in FIGS. 2 and 3a, the foil blade inserts 12 are shaped incross section somewhat like the letter T. The top bearing surface 18 andleading underface surface 24 intersect to form leading edge 26. A lower,horizontal lip surface 28, substantially parallel to surface 18, extendsinwardly from leading surface 24 and corresponding leading edge surface9 on the foil body and is supported against a corresponding mountingsurface 30 on foil body 16. In similar fashion, a second surface 32 onblade insert 12 extends downwardly from the top bearing surface 18 at anacute angle with both wire 20 traveling in the machine directionandsurfaces 19, 28.

Edge a is flush with top surface 19 of foil body 16. Surface 32 issupported on corresponding mounting surface 33 in the groove of foilbody 16.

As shown in FIGS. 3 and 4, a notch 48 is formed in the lower portion ofgroove 14, coextending therewith, substantially vertical with surface30.

A commercially available continuous wave spring 40 is inserted along theleading wall 38 of notch 48 to urge the foil blade insert 12 into seatedengagement with foil body 16 in the machine direction. In amodification, wave spring 40 is made up of individual units alignedwith, and corresponding in number to, the foil blade inserts 12 to urgeeach of them into seated engagement with the foil body.

The lower blade lip surface has coplanar portions 28, 28 which extend oneither side of the downwardly extending portion 46 of foil blade 12a andis supported on a corresponding coplanar portions of mounting surface30, 30' in groove 14a. The vertical rib portion 46 of blade insert 12,being narrower than notch 48, does not contact the side walls 38, 49 orbottom wall 36 of notch 48. In the T shaped foil blade embodiment, onlydimensions 43a and 44a are held to close machined tolerances such asabout i 0.0005 inch to about 0.00l inch to accurately fit the foil bladeinto the foil body. Surfaces 28, 32 on the foil blade insert andsurfaces 30, 33 on the foil body are the only surfaces, except the topbearing surface 18 and underface surface 24 on the foil blade, whichneed be made smooth or finished. Accordingly, surfaces 28, 32, 30, 33are referred to as finished mounting surfaces. None of the surfaces ondownwardly extending rib portion 46, including rib bottom surface 34, ornotch 48 have to be finished in any particular manner.

Surface 19 is substantially coplanar with aligned top bearing surfaces18 of foil blade inserts 12. It can be seen that edges 26 and surfaces18, 24 are aligned longitudinally along the foil body lengthextendingtransversely across the machine. Usually, the leading edgeportion of surface 18 is beveled or arcuately turned downwardly slightlyto form a small (i.e. 05) acute angle 21 with the plane of the oncomingwire 20. In the case of an arcuately curved surface, the angle 21 wouldbe measured between the plane of the wire and a plane tangent to thesurface at the leading edge. In operation, top bearing surface 18 isbrought into contact with wire 20 and the foil body may be rotated aboutsupporting journals 17 such that foil body top surface 19 may divergefrom the plane of the wire 20 at a small angle (i.e., about 05),depending on the position of leading edge 26. Liquid is skimmed off theunderside of wire 20 by face surface 24 and a slight negative pressuredifferential is formed in the gap between wire 20 and surface 19 whichinduces liquid to flow therebetween and out of the wire.

The foil blade insert 12b in FIG. 5 has the general cross sectional areashape of a parallelogram. A notch 50 angles upwardly and forwardly, inthe direction of wire 20b travel, from the bottom surface 28b of foilblade 12b. Surface 28b, 28b has coplanar portions extending on eitherside of notch 50 to bear on corresponding portions of surface 30b, 30b.A communicating notch 48b is in the bottom of groove 14b and a L- shapedspring 52, one for each segment of blade insert 12b, is positioned inthese notches to urge foil blade 12b into seated engagement with foilbody 16b in the direction of wire 20b travel. As in the T shapedembodiment, only dimensions43b and 44b are held to close tolerances toensure an accurate fit with foil body 16b and coplanar alignment betweensurfaces 18b and 19b along flush edge 45b. Also, as with the T-shapedinsert, surfaces 28b, 32b, 30b, 33b, are referred to as finishedmounting surfaces.

In each of the embodiments shown in FIGS. 3, 4 and 5, grooves 14, 14a,14b and notches 48, 48b extend continuously for the foil length which,in operating position, is transverse to the machine direction of wiretravel 20. Foil blade inserts 12 are provided in two standard lengths ofIO and 12 inches which allows the foil blade to be built up to anylength within two inches. Similarly, wave springs 40, 40a and rightangle spring 52 coextend in the grooves or notches in which they arepositioned as they urge the foil blade inserts into operating engagementwith the foil body. There are no press or interference fits between thefoil blade inserts and the foil body since only springs are used tomount the foil blades to the foil body. To replace one or all of thefoil blade inserts, one or both of the end springs 25 are removed andthe foil blade inserts are slid into or out of position. No unscrewing,pulling dovetailed or force fit wedges or breaking adhesive bonds isnecessary.

When the papermaking machine is in operation and the wire is moving indirection 20, the force of springs 40, 40a, 52 is complimented by theforce component of the wire contacting the top bearing surfaces 18, todrive the foil blade surfaces 28, 32 into the wedge formed betweenmounting surfaces 30, 33 on the foil body. In each of the embodiments,back face 35 is formed on blade insert 12 so that a gap 39 in groove 14is formed between the corresponding inner face 37 on the foil body andblade insert, thereby obviating the necessity for finishing these facesto expensive machined tolerances. When the machine is shut down forcleaning or repairs, springs 40, 40a, 52 hold the blade foil elements inposition against the foil body, and end springs 25 hold the butt jointsof the adjoining foil blade segments together against one another. Sinceno spring 40, 40a, 52 or foil blade segments are fixedly secured to oneanother or to the foil body, any change in length due to relativethermal expansion or contraction between foil blades and foil body willhave no effect on the security with which these parts are positioned inplace. The foil blade inserts are secured to the foil body solely withsprings. It should be noted that, with respect to the embodiments shownin FIGS. 4 and 5, notches 48, 48b and 50 need not be held to any costlymachined tolerances since they only provide means to mount the springswhich attach the foil blade segments to the foil body and do not serveto align these parts.

Various abrasion resistant materials, such as aluminum oxide, chromiumoxide, tungsten carbide and silicon carbide have been used for the foilblade inserts and, undoubtedly, other materials will also functionsatisfactorily. Aluminum oxide is the preferred material for the foilblade inserts. The foil bodies are generally made of stainless steel toresist corrosion, although other corrosion resistant materials, such asplastic, can be used.

Some prior art embodiments of foils and the methods used to mount themare shown in FIGS. 6a-6e. FIG. 6 shows what is believed to be the firstof the modern foils wherein a stainless steel foil 54 is coated with anabrasion resistant coating 57 on its top bearing surface 58. Foil 54 wasas long as the foil body 55 on which it was mounted and had to beremoved and returned to the coating manufacturer when coating 57 wasworn or damaged. Face edge 56 was not coated with an abrasion resistantmaterial.

In FIG. 6b, a dovetailed, abrasion resistant insert 60 is press fit intothe foil body 54b at a location where its top bearing surface 58bcontacted the wire traveling in direction 20b. This did not providesufficient wear resistance for the leading edge so the foil blade insertshown in FIG. 6c was developed which had the face edge 56c and topbearing surface 58c of abrasion resistant material. If this foil bladeis screwed into the body, it is very difficult to remove. If it isadhesively secured and loosens, it can fall out of the foil body duringcleanup when the machine is stopped.

FIG. 6d shows a foil similar to that of FIG. 6a except the entire top58a is made of abrasion resistant material in an attempt to eliminateproblems in mounting a foil blade into the foil body. This was far morecostly than a similar insert made of abrasion resistant material.

FIG. 62 illustrates a foil having a dovetailed blade wherein a costlyand complicated movable mechanical wedge apparatus 62 locks the foilblade 586 into position against the direction of wire travel 2le. Thus,any looseness in the wedge apparatus 62 will allow the blade to moveand, possibly, vibrate in operation which is, of course, extremelydetrimental to good paper formation.

The common problem with prior art foils is that they either require thewhole foil to be removed from the machine for repair or the abrasionresistant insert is difficult to remove. In the case of dovetailedinserts, the foil blade inserts are very difficult to remove forreplacement. Anyone familiar with dovetailed joints can well appreciatethe difficulty in separating two pieces 20 to 30 feet long which aresnugly fit together.

Thus, it will be seen that an invention has been set forth whichincorporates the features and achieves the objectives desired. It shouldbe understood that while the specific embodiment referred to a foil on apapermaking machine, the foil could operate on other web formingmachines, such as non-woven fabrics, with equal efficiency. Also whilethe position of the foil relative to the wire would not changesignificantly, the foil could operate as well against a wire moving atan angle to a horizontal plane or even vertically. Further, while nomaterial has been referred to in conjunction with the wire, it isunderstood the wire could be metallic, plastic or made of syntheticfibers.

We claim:

1. An elongated drainage foil for removing liquid from a contiguousdrainage wire traveling in a given direction on a web making machine,the foil extending transversely to the direction of wire travel when inoperating position, comprising:

a. a body member having top and leading edge surfaces extending alongthe length thereof and having a coextending groove in the intersectionof said top and leading edge surfaces, said groove having just twomounting surfaces which are inclined one to the other;

b. a foil blade insert member polyhedron disposed within said groovehaving abrasion resistant leading and top bearing surface faces forminga leading edge toward the oncoming traveling wire direction, said topbearing surface face being flush with said top surface and positionableagainst the wire, and

having just two inclined mounting surfaces engaged with respective onesof said groove mounting surfaces;

c. resilient means interposed between said body and foil blade memberswithin the groove urging said foil blade member against said body memberin the direction of wire travel, thus cooperating with the two mountingsurfaces to provide the sole means of attaching the foil blade insertmember to the body member.

2. A drainage foil as set forth in claim 1, wherein:

said foil blade insert member comprises at least two similar segmentedparts aligned end to end in said groove transversely to the direction ofwire travel; and

restraining means mounted on said body member and bearing against theoutermost ends of said foil blade member parts, thereby maintainingabutting contact between adjoining ends thereof.

3. The drainage foil as set forth in claim 2, wherein:

said adjoining ends of adjacent foil blade member parts have buttjoints.

4. The drainage foil as set forth in claim 2, wherein:

said resilient means comprises individual units, each of which bearsagainst corresponding ones of said foil blade member parts.

5. The drainage foil as set forth in claim 2, wherein:

the leading portion of said top bearing surface turns downwardly at asmall acute angle with respect to the plane of the wire in the oncomingdirection of its travel.

6. The drainage foil as set forth in claim 2, wherein:

the cross section of the foil blade member polyhedron is in the shape ofa parallelogram when viewed through a plane normal to its leading edgeand top surface;

one of said foil blade member inclined surfaces is substantiallyparallel with said top bearing surface face;

another of said foil blade member inclined surfaces is inclined at anacute angle with the wire in its direction of travel such that the forceof the wire urges the foil blade member into wedging engagement with thebody member;

a notch is in said body member groove coextending therewith;

said foil blade member includes a corresponding coextending notch incommunication with said body member notch;

said resilient means comprises a spring mounted within both said notchesand coextending therealong.

7. The drainage foil as set forth in claim 6, wherein:

said resilient means comprises individual units, each of which bearsagainst corresponding ones of said foil blade member parts.

8. The drainage foil as set forth in claim 6, wherein:

the leading portion of said top bearing surface turns downwardly at asmall acute angle with respect to the plane of the wire in the oncomingdirection of its travel.

9. The drainage foil as set forth in claim 2, wherein:

the foil blade member is in the general shape of a T,

having a substantially horizontal and vertical portions, the top ofwhich horizontal portion comprises the top bearing surface;

one of the body member mounting surfaces is substantially parallel withsaid top bearing surface face;

a notch is in said body member groove coextending therewith;

the vertical portion of said foil blade member is positioned within saidnotch such that a gap is formed between its leading edge and therespective leading edge of said notch, and the bottom surface of saidhorizontal portion is in bearing engagement with one of the body membermounting surfaces;

the resilient means comprises a wave spring positioned within said gap,coextending therein.

10. The drainage foil as set forth in claim 9, wherein:

the horizontal portion has a second surface having an 'upper edge flushwith said body member upper surface, and extends downwardly from saidedge at an acute angle with the wire in its direction of travel andengages another corresponding mounting surface in said body member. 11.The drainage foil as set forth in claim 9, wherein: the leading portionof said top bearing surface turns downwardly at a small acute angle withrespect to the plain of the wire in the oncoming direction of itstravel.

1. An elongated drainage foil for removing liquid from a contiguousdrainage wire traveling in a given direction on a web making machine,the foil extending transversely to the direction of wire travel when inoperating position, comprising: a. a body member having top and leadingedge surfaces extending along the length thereof and having acoextending groove in the intersection of said top and leading edgesurfaces, said groove having just two mounting surfaces which areinclined one to the other; b. a foil blade insert member polyhedrondisposed within said groove having abrasion resistant leading and topbearing surface faces forming a leading edge toward the oncomingtraveling wire direction, said top bearing surface face being flush withsaid top surface and positionable against the wire, and having just twoinclined mounting surfaces engaged with respective ones of said groovemounting surfaces; c. resilient means interposed between said body andfoil blade members within the groove urging said foil blade memberagainst said body member in the direction of wire travel, thuscooperating with the two mounting surfaces to provide the sole means ofattaching the foil blade insert member to the body member.
 1. Anelongated drainage foil for removing liquid from a contiguous drainagewire traveling in a given direction on a web making machine, the foilextending transversely to the direction of wire travel when in operatingposition, comprising: a. a body member having top and leading edgesurfaces extending along the length thereof and having a coextendinggroove in the intersection of said top and leading edge surfaces, saidgroove having just two mounting surfaces which are inclined one to theother; b. a foil blade insert member polyhedron disposed within saidgroove having abrasion resistant leading and top bearing surface facesforming a leading edge toward the oncoming traveling wire direction,said top bearing surface face being flush with said top surface andpositionable against the wire, and having just two inclined mountingsurfaces engaged with respective ones of said groove mounting surfaces;c. resilient means interposed between said body and foil blade memberswithin the groove urging said foil blade member against said body memberin the direction of wire travel, thus cooperating with the two mountingsurfaces to provide the sole means of attaching the foil blade insertmember to the body member.
 2. A drainage foil as set forth in claim 1,wherein: said foil blade insert member comprises at least two similarsegmented parts aligned end to end in said groove transversely to thedirection of wire travel; and restraining means mounted on said bodymember and bearing against the outermost ends of said foil blade memberparts, thereby maintaining abutting contact between adjoining endsthereof.
 3. The drainage foil as set forth in claim 2, wherein: saidadjoining ends of adjacent foil blade member parts have butt joints. 4.The drainage foil as set forth in claim 2, wherein: said resilient meanscomprises individual units, each of which bears against correspondingones of said foil blade member parts.
 5. The drainage foil as set forthin claim 2, wherein: the leading portion of said top bearing surfaceturns downwardly at a small acute angle with respect to the plane of thewire in the oncoming direction of its travel.
 6. The drainage foil asset forth in claim 2, wherein: the cross section of the foil blademember polyhedron is in the shape of a parallelogram when viewed througha plane normal to its leading edge and top surface; one of said foilblade member inclined surfaces is substantially parallel with said topbearing surface face; another of said foil blade membeR inclinedsurfaces is inclined at an acute angle with the wire in its direction oftravel such that the force of the wire urges the foil blade member intowedging engagement with the body member; a notch is in said body membergroove coextending therewith; said foil blade member includes acorresponding coextending notch in communication with said body membernotch; said resilient means comprises a spring mounted within both saidnotches and coextending therealong.
 7. The drainage foil as set forth inclaim 6, wherein: said resilient means comprises individual units, eachof which bears against corresponding ones of said foil blade memberparts.
 8. The drainage foil as set forth in claim 6, wherein: theleading portion of said top bearing surface turns downwardly at a smallacute angle with respect to the plane of the wire in the oncomingdirection of its travel.
 9. The drainage foil as set forth in claim 2,wherein: the foil blade member is in the general shape of a T, having asubstantially horizontal and vertical portions, the top of whichhorizontal portion comprises the top bearing surface; one of the bodymember mounting surfaces is substantially parallel with said top bearingsurface face; a notch is in said body member groove coextendingtherewith; the vertical portion of said foil blade member is positionedwithin said notch such that a gap is formed between its leading edge andthe respective leading edge of said notch, and the bottom surface ofsaid horizontal portion is in bearing engagement with one of the bodymember mounting surfaces; the resilient means comprises a wave springpositioned within said gap, coextending therein.
 10. The drainage foilas set forth in claim 9, wherein: the horizontal portion has a secondsurface having an upper edge flush with said body member upper surface,and extends downwardly from said edge at an acute angle with the wire inits direction of travel and engages another corresponding mountingsurface in said body member.